Even in the most sensitive part of human retina, the fovea, perception is not uniform. To compens... more Even in the most sensitive part of human retina, the fovea, perception is not uniform. To compensate for such non-uniformity, tiny fixational microsaccades direct the optimal foveal locus to relevant parts of the fixated scene, similarly to larger exploratory saccades but on a miniature scale.
bioRxiv (Cold Spring Harbor Laboratory), Jul 3, 2022
Visual perceptual learning is traditionally thought to arise in visual cortex. However, typical p... more Visual perceptual learning is traditionally thought to arise in visual cortex. However, typical perceptual learning tasks also involve systematic mapping of visual information onto motor actions. Because the motor system contains both effector-specific and effector-unspecific representations, the question arises whether visual perceptual learning is effector-specific itself, or not. Here, we study this question in an orientation discrimination task. Subjects learn to indicate their choices either with joystick movements or with manual reaches. After training, we challenge them to perform the same task with eye movements. We dissect the decision-making process using the drift diffusion model. We find that learning effects on the rate of evidence accumulation and the decision criteria depend on effectors, albeit not fully. This suggests that during perceptual learning, visual information is mapped onto effector-specific integrators. Overlap of the populations of neurons encoding motor plans for these effectors may explain partial generalization. Taken together, visual perceptual learning is not limited to visual cortex, but also affects sensorimotor mapping at the interface of visual processing and decision making.
Area V1 is known for its neural cell density and intricate histology. Physiological recordings, h... more Area V1 is known for its neural cell density and intricate histology. Physiological recordings, however, often are not integrated into this complex anatomy. We have previously shown, in alert monkeys, that physiological properties of single cells reflect an alternating arrangement of anatomical layers. Here we report how orientation selectivity is related to the cortical layers and to the cell properties of spontaneous activity, classical receptive field (CRF) size, and spatial organization. Recordings were made from single cells in area V1 of alert monkeys performing a fixation task. The cells' spatial organization was studied with drifting increment and decrement bars while compensating for fixational drift. Orientation selectivity was measured by the orientation tuning curve bandwidth and by circular variance. Orientation selectivity by either measure was clearly correlated with CRF size and spontaneous activity but not with overlap of increment and decrement zones (Simple/Complex) or with relative modulation in response to sinusoidal gratings. The former 3 measures were strongly predicted by the layer of origin such that small CRFs, low spontaneous activity, and a high degree of orientation selectivity were found in the output layers 2/3, 4B and 5 while the reverse was true for the input layers 4A, 4C and 6. We conclude that the conjunction of these physiological measures with their anatomical locations reflect interactions between excitatory and inhibitory mechanisms specific to each lamina. When excitation is stronger than inhibition, large CRFs, high spontaneous activity and a low degree of orientation tuning are found. When inhibition becomes dominant, CRFs shrink, spontaneous activity almost disappears and orientation selectivity is high.
Many real-world decisions in social contexts are made while observing a partner's actions. To stu... more Many real-world decisions in social contexts are made while observing a partner's actions. To study dynamic interactions during such decisions, we developed a setup where two agents seated face-to-face to engage in game-theoretical tasks on a shared transparent touchscreen display ('transparent games'). We compared human and macaque pairs in a transparent version of the coordination game 'Bach-or-Stravinsky', which entails a conflict about which of two individuallypreferred opposing options to choose to achieve coordination. Most human pairs developed coordinated behavior and adopted dynamic turn-taking to equalize the payoffs. All macaque pairs converged on simpler, static coordination. Remarkably, two animals learned to coordinate dynamically after training with a human confederate. This pair selected the faster agent's preferred option, exhibiting turn-taking behavior that was captured by modeling the visibility of the partner's action before one's own movement. Such competitive turn-taking was unlike the prosocial turn-taking in humans, who equally often initiated switches to and from their preferred option. Thus, the dynamic coordination is not restricted to humans but can occur on the background of different social attitudes and cognitive capacities in rhesus monkeys. Overall, our results illustrate how action visibility promotes the emergence and maintenance of coordination when agents can observe and time their mutual actions. Editor's evaluation This study investigates and compares spontaneous turn-taking behavior in pairs of macaque monkeys and human participants. The study is well-designed and uses a novel format for dynamic interaction. The analyses are rigorous and support the overall conclusion that there are differences between species in their tendencies toward cooperative, mutually beneficial behaviors, with humans exhibiting more prosocial tendencies. This finding, as well as the rich description of pair interactions in each species, is likely to be relevant to a broad range of researchers interested in social behavior.
BOLD fMRI dynamics in monkeys reflects spatial decisions in free-choice and reward context tasks
Neuroscience Research, 2009
We investigated voluntary decision-making and motor planning in monkeys with time-resolved event-... more We investigated voluntary decision-making and motor planning in monkeys with time-resolved event-related high-field fMRI. We previously found strong contralateral tuning of frontoparietal BOLD activity during a memory saccade task. Here we used a spatial decision task to assess the dynamics of response selection. Two equally rewarded targets were presented and after a delay monkeys could select either location. The contralateral build-up of BOLD activity during the delay reflected the monkeys’ choices, and different areas signaled the decision at different times. Internal spatial preferences were reflected in the inter-hemispheric imbalance of left/right spatial representations. These patterns imply mutually suppressive interactions between two response options. Next, we introduced a reward context associated with target colors. The behavioral preference for large expected rewards was paralleled by a stronger delay period activity, supporting prospective evaluation of goal-directed actions. We suggest a common mechanism integrating internal and external variables during oculomotor decisions.
this is a general mechanism in the many fishes that presumably have the Schreckstoff system-let a... more this is a general mechanism in the many fishes that presumably have the Schreckstoff system-let alone in zebrafish about whose ecology deplorably little is known-remains an open question. The chemical nature of the Schreckstoff component identified by Mathuru and colleagues [3] and its being a constituent of mucus do suggest that the alarming function could be a secondary by-product. But then, what about the club cells? Surprisingly, there is evidence that their alarm function might also only be secondary. When fathead minnows are exposed to parasites, pathogens or UV light, they increase the number of club cells in the skin, an effect that is inhibited by immuno-suppresion [20]. So, after all, the Schreckstoff could just be a by-product of other protective functions that enhance fitness of the bearer-much like its serendipitous discovery was the by-product of a summer holiday and the study of hearing in fish. And much like that first minnow that von Frisch cut, the presumed evolutionary enigma of Schreckstoff might just disappear. Oh, by the way, did we mention what the new Schreckstoff component was? Oligosaccharides of chondroitin-4-sulfate and chondroitin-6-sulfate.
Wager-specific proportions of trials and slopes for the five difficulty levels The Supplementary ... more Wager-specific proportions of trials and slopes for the five difficulty levels The Supplementary Figure S1A and Supplementary Figure S1B illustratefor PreDW and PDW, respectivelythe wager-specific proportions of correct and incorrect trials separately for the five difficulty levels. These proportions resulted in the slope-based measures illustrated in the third row of the Supplementary Fig. S1C and in the Figure 10. To test, within each difficulty level, if slope-correct was different from slope-incorrect depending on the trial type (PreDW or PDW), we performed two-way ANOVAs for repeated measures. In none of the difficulty levels PreDW slope-correct was significantly different from PreDW slope-incorrect (p>0.05; Supplementary Fig. S1A), indicating reliable baselines for the five
Despite many years of intense research, there is no strong consensus about the role of the latera... more Despite many years of intense research, there is no strong consensus about the role of the lateral intraparietal area (LIP) in decision making. One view of LIP function is that it guides spatial attention, providing a "saliency map" of the external world. If this were the case, it would contribute to target selection regardless of which action would be performed to implement the choice. On the other hand, LIP inactivation has been shown to influence spatial selection and oculomotor metrics in free-choice decisions, which are made using eye movements, arguing that it contributes to saccade decisions. To dissociate between a more general attention role and a more effector specific saccade role, we reversibly inactivated LIP while non-human primates freely selected between two targets, presented in the two hemifields, with either saccades or reaches. Unilateral LIP inactivation induced a strong choice bias to ipsilesional targets when decisions were made with saccades. Interestingly, the inactivation also caused a reduction of contralesional choices when decisions were made with reaches, albeit the effect was less pronounced. These findings suggest that LIP is part of a network for making oculomotor decisions and is largely effector-specific in free-choice decisions. Over the past several years, a growing body of studies provided evidence that the lateral intraparietal area (LIP), a subdivision of the inferior parietal lobule (IPL), is involved in various computations related to decision making 1,2. The evidence is mainly based on neurophysiological recordings showing that LIP neurons integrate many factors related to choices 2,3 , represent decision-related variables, such as expected reward and outcome probability 4-8 , and accumulate sensory evidence over time for making perceptual judgments 9,10. Along the same lines, pharmacological inactivation studies showed that temporary lesions in LIP caused a reduction of contralesional choices-i.e., the visual space represented by the silenced neurons-in oculomotor free-choice decisions 11,12. Remarkably, silencing LIP neurons in motion discrimination tasks did not have any effect on the decision process 13 , questioning the role of LIP in perceptual decisions 14,15. Similar findings have also been reported in rodents, where inactivating PPC neurons whose activity was correlated with decision-related variables affected free-choices but not perceptual judgments 16. While these studies revealed a key role of LIP in oculomotor free-choices, it is still unclear whether it contributes to decision-making irrespective of which action is performed to implement the selected option (i.e., effector non-specific hypothesis) or it is involved mainly in oculomotor decisions (i.e., effector-specific hypothesis). An effector non-specific deficit after inactivation would be consistent with the attention role for LIP in decision making, in which LIP guides the allocation of spatial attention to select a target in space, regardless on how this target will be used 17-21. To dissociate between a more general attention role and a more effector-specific saccade role, we reversibly inactivated LIP while two macaque monkeys performed memory-guided saccade or reach movements to either a single target or selected one of two targets presented simultaneously in both hemifields. Consistent with previous studies 11,12,22,23 , after silencing LIP neurons the animals were less likely to select saccade targets located in the contralesional hemifield. At the same, LIP inactivation caused a reduction of contralesional reach choices, albeit the effect was less pronounced. The sensory, memory and motor components of the task remained largely intact, besides a reduction of the reach performance in one animal for movements to both visual hemifields. Overall, our results provide direct evidence that LIP is primarily saccade-specific in free-choice decisions,
Visual processing depends on rapid parsing of global features followed by analysis of fine detail... more Visual processing depends on rapid parsing of global features followed by analysis of fine detail. A new study suggests that this transformation is enabled by a cycle of saccades and fixational drifts, which reformat visual input to match the spatiotemporal sensitivity of fast and slow neuronal pathways.
Real-world agents, humans as well as animals, observe each other during interactions and choose t... more Real-world agents, humans as well as animals, observe each other during interactions and choose their own actions taking the partners' ongoing behaviour into account. Yet, classical game theory assumes that players act either strictly sequentially or strictly simultaneously without knowing each other's current choices. To account for action visibility and provide a more realistic model of interactions under time constraints, we introduce a new gametheoretic setting called transparent games, where each player has a certain probability of observing the partner's choice before deciding on its own action. By means of evolutionary simulations, we demonstrate that even a small probability of seeing the partner's choice before one's own decision substantially changes the evolutionary successful strategies. Action visibility enhances cooperation in an iterated coordination game, but reduces cooperation in a more competitive iterated Prisoner's Dilemma. In both games, "Win-stay, loseshift" and "Tit-for-tat" strategies are predominant for moderate transparency, while a "Leader-Follower" strategy emerges for high transparency. Our results have implications for studies of human and animal social behaviour, especially for the analysis of dyadic and group interactions.
The pulvinar complex is interconnected extensively with brain regions involved in spatial process... more The pulvinar complex is interconnected extensively with brain regions involved in spatial processing and eye movement control. Recent inactivationstudieshaveshownthatthedorsalpulvinar(dPul)playsaroleinsaccadetargetselection;however,itremainsunknownwhetheritexerts effects on visual processing or at planning/execution stages. We used electrical microstimulation of the dPul while monkeys performed saccade tasks toward instructed and freely chosen targets. Timing of stimulation was varied, starting before, at, or after onset of target(s). Stimulation affected saccade properties and target selection in a time-dependent manner. Stimulation starting before but overlapping with target onset shortened saccadic reaction times (RTs) for ipsiversive (to the stimulation site) target locations, whereas stimulation starting at and after target onset caused systematic delays for both ipsiversive and contraversive locations. Similarly, stimulation starting before the onset of bilateral targets increased ipsiversive target choices, whereas stimulation after target onset increased contraversive choices. Properties of dPul neurons andstimulationeffectswereconsistentwithanoverallcontraversivedrive,withvaryingoutcomescontingentuponbehavioraldemands.RTand choice effects were largely congruent in the visually-guided task, but stimulation during memory-guided saccades, while influencing RTs and errors, did not affect choice behavior. Together, these results show that the dPul plays a primary role in action planning as opposed to visual processing, that it exerts its strongest influence on spatial choices when decision and action are temporally close, and that this choice effect can be dissociated from motor effects on saccade initiation and execution.
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